USA Today reported over the weekend that the Army has been told to plan to lop off 100,000 soldiers if the automatic budget cuts known as sequestration continue until the end of the decade. Army brass are coming to terms with what a force of 420,000 could and could not do. It has about 530,000 soldiers now. The other services will be taking hits, too, according to a senior Pentagon official, who spoke on condition of anonymity because the details are not public.

First, what smaller armed forces probably won’t do: wage long-term wars. A few years ago, the White House declared in its strategy that the Pentagon would no longer maintain forces big enough to conduct stability operations, such as those in Iraq and Afghanistan. Don’t forget how to fight counterinsurgencies, the strategic guidance states. Just don’t plan on having forces big enough to sustain them over a long period of time.

Sequestration, though the Pentagon loathes it for cutting fat, muscle and bone, does provide the excuse to shrink its forces and budgets to align with the White House strategy.

What would a smaller military look like? Defense Secretary Chuck Hagel has said he favors one that is more agile and equipped with the latest weapons. To that end, the Pentagon is liquidating much of its $40 billion fleet of Mine Resistant Ambush Protected vehicles, the signature truck of the wars in Iraq and Afghanistan. They’re heavy and lumbering and associated with wars of occupation. Definitely passe.

How would it fight? A glimpse of the military’s future can be seen in Africa.

The Army and Marine Corps have created fast-reaction units to respond to crises such as recent evacuation of Americans from war-torn South Sudan.

The units — the Army’s East Africa Response Force and the Marines’ Special Purpose Marine Air-Ground Task Force for Crisis Response — were formed after the attack on the State Department mission in Benghazi that killed four Americans, including the ambassador. A Senate report released last week noted that “there were no U.S. military resources in position to intervene in short order in Benghazi to help defend” the American facilities there. The report also points out that the vast region is covered by few U.S. troops, making it unlikely the Pentagon can respond quickly to “all potential crises” in the region.

Gen. David Rodriguez, who leads Africa Command for the Pentagon, said earlier this month that troops from the new units have been deployed to South Sudan, and that the military also has a small group of troops helping the French in Mali. Last week, Air Force and Army troops helped transport 850 Rwandan troops and their equipment into the Central African Republic for a peacekeeping mission.

The missions have risks. Four Navy SEALs were wounded last month trying to evacuate Americans from South Sudan. The troops’ Osprey aircraft was hit by gunfire, and the American had to be evacuated by U.N. personnel the next day.

The brass understand the need to remake themselves.

“We’ll have to embrace change or risk irrelevance,” Gen. Martin Dempsey, chairman of the Joint Chiefs of staff, told an audience at the National Defense University last week.